The invention is in the field of isostatic presses and the process of using same.
U.S. Pat. No. 3,992,912 to Jonsson issued on Nov. 23, 1976 and discloses an isostatic press in which workpieces are enclosed in a pressure vessel filled with a liquid and closed by a lid. The vessel is pressurized after it is placed in a frame adapted to absorb substantially vertical forces. The lid or top cover is moveable substantially vertically in relation to the pressure vessel after the vessel has been introduced into the frame.
The ""912 patent to Jonsson describes known isostatic presses and states that they fall into two general categories. The first category involves small diameter pressure vessels having lids which can be screwed into the pressure vessel. The other category is applicable to larger pressure vessels where the lids must be held in place or supported by another structure such as a yoke or frame. Typically a yoke or frame can be used for the additional support which is required. The yoke or frame is typically made out of high strength metal which can resist substantial tensile forces without significant deformation. Use of the yoke or frame, however, requires that the pressure vessel be removed from the yoke or frame each time a new workpiece is to be introduced to the vessel. Efficiency in loading and unloading the pressure vessel is lowered because of the need to remove the pressure vessel from the frame. Further, process connections to the pressure vessel must be disconnected every time the vessel is loaded and unloaded. These process connections must be secure as the pressure in the isostatic pressure vessels can reach 150,000 psi. Every time a process connection is made and broken, the seal therein is slightly degraded.
The ""912 patent to Jonsson discloses a frame and a pressure vessel within the frame. Although the pressure vessel is moved horizontally every cycle, the lid is moved substantially vertically by two cylinders 6, 7. See, FIG. 1. The press shown in the drawing comprises a frame stand 1 into which a cylindrical high-pressure vessel 2 is introduced. The pressure vessel 2 is provided with a bottom closure 3 and a top lid 4. A pressure fluid pipe 5 communicates with the top lid 4, which is vertically moveable by two double-acting cylinders 6, 7 disposed on each side of the frame. Spacer plate 8 is inserted into the frame 2 between the top lid 4 and the upper portion of the frame and is laterally displaceable along a track 9 as illustrated in FIGS. 2 and 3 which also illustrate the prior art. Spacer plate 8 is displaced by a hydraulic cylinder 10 actuating two lever arms 11, 12, respectively, the outer ends of which include pins 13 and 16, respectively. The pins cooperate with grooves formed in panels 14 and 15, respectively, projecting from the plate.
The ""912 patent to Jonsson discloses an alternative embodiment where the top lid is fixed in relation to the upper yoke or frame and the pressure vessel is lifted toward the fixed top lid every cycle. In the alternative embodiment, the pressure vessel must be horizontally moved out of the frame each cycle for loading and unloading. Spacer plates are used in the alternative embodiment as well except they are placed underneath the pressure vessel and reside between the bottom closure of the vessel and the lower yoke of the frame.
U.S. Pat. No. 4,563,143 to Pettersson issued Jan. 7, 1986 discloses a pressure vessel or chamber 1 affixed to the top portion of a yoke or frame. A die and a closure are raised through a combination of pistons and are secured in place by pivoting legs which are also piston operated. The die/closure is brought into the isostatic press horizontally by a conveyor.
Considerable motion is necessary to place workpieces in prior art isostatic presses. Some isostatic presses involve the use of a rail 402 as illustrated in FIG. 4 to move a top portion 401 of the yoke or frame away from the pressure vessel. FIG. 4 is a diagrammatic representation of a large prior art isostatic press. An example of a large isostatic press is illustrated at http://www.kinzoku.co.jp/hot_.html. Pistons mounted on the yoke or frame 401 are used to vertically lift the top cover 404 or lid from the isostatic press and then guide the top half of the yoke 401 horizontally away from the pressure vessel thus enabling access to the pressure vessel. Hydraulic pistons and the like 405 may be used in regard to moving and securing the lid.
Referring to FIG. 4, two motions are necessary to remove the lid from the pressure vessel. First, the lid must be lifted vertically. Next, the lid must be moved horizontally.
To access the work piece from the pressure vessel, a horizontal motion is necessary to position one""s self or a robot arm over the pressure vessel opening. Next, a vertical motion and a horizontal motion are necessary to remove the workpiece(s) from the pressure vessel. The steps are repeated in the reverse order to load the workpiece(s) into the pressure vessel. Each motion in the pressurization cycle reduces the efficiency thereof.
Isostatic presses are used in processes which require fluid and/or fluid and gas to be pressurized at pressures up to 150,000 psia. The processes are too numerous to name. Likewise, the workpieces treated in isostatic presses are too numerous to name.
Therefore, there is a need for an isostatic press which is highly efficient and which reduces the motion necessary to load and unload the workpieces from the pressure vessel.
An isostatic press is disclosed and comprises: a yoke; a bottom cover affixed to the yoke; a top cover affixed to the yoke; and, a generally cylindrical body moveable between a first position and a second position. Preferably, the yoke includes a tongue upon which the bottom cover is mounted. In the first position the generally cylindrical body rests on the yoke and extends vertically therefrom and resides circumferentially around the bottom portion of the bottom cover. However, the body does not cover or occlude the top surface of the bottom cover. The bottom cover resides atop a tongue of the yoke. The generally cylindrical body is driven upwardly from the first position to the second position where it abuts the top cover. In the second position, a chamber is formed by the bottom cover, the top cover and the body. The body is secured in place by the driving mechanism and by two latches which engage with a plate affixed to the body. The driving mechanism may be any type of linear actuator.
In the second position, the chamber is pressurized and the load is absorbed by the top cover, bottom cover and the cylindrical body. The body may be a perfect cylinder or it may have interior portions thereof having different diameters. End portions of the cylinder have a smaller inside diameter enabling more effective sealing of the pressure vessel when the body is in the second position. Further, a larger inside diameter in the intermediate portion of the vessel avoids wear and tear on the seals as the body is raised to the second position from the first position and vice-versa.
An isostatic press comprising a bottom cover, a top cover, and, a cylindrically shaped body having axially aligned centers is disclosed. The generally cylindrically shaped body is axially movable between first and second positions. When the cylindrically shaped body is axially moved to the second position, the inside wall of the cylindrical body engages the U-shaped seals which reside in circumferential recesses located about the top and bottom covers. Alternatively, conventional polymeric O-ring seals may be employed.
At least one process connection passageway exists in the top cover or in the bottom cover. Several passageways through the top and/or bottom cover may also be employed as desired by the user for the particular process employed. Since the top cover and the bottom cover are affixed to the yoke (sometimes referred to as the frame), the process connections do not have to be broken upon loading and unloading of the workpieces. This lowers the maintenance of the system and greatly increases the cycle frequency and efficiency.
A process for isostatically pressing a workpiece in an isostatic press having a yoke, a bottom cover supported by the yoke, a top cover supported by the yoke, and a body moveable between a first position and a second position, comprising the steps of: placing the workpiece on the bottom cover; moving the body from the first position to said second position; and, pressurizing the workpieces is disclosed. Further steps of depressurizing the workpieces and moving the body from the second position to the first position are necessary for completing the cycle. An additional step of removing the workpieces from the top of the bottom cover is necessary to unload the pressure vessel or pressure chamber.
Accordingly, it is an object of the invention to provide an isostatic press which minimizes the motion necessary for loading and unloading the workpieces to be pressurized.
Another object of the invention is to minimize the cycle time for pressurizing the workpieces. The cycle time may be defined as the amount of time measured from the time a workpiece is loaded into the press until the next workpiece is loaded into the press.
Another object of the invention is to provide an isostatic press which does not require process connections to be broken during unloading of the workpieces from the press.
Another object of the invention is to provide an isostatic press which has top and bottom covers fixed to the frame/yoke.
Another object of the invention is to provide an isostatic press having a body secured to the frame/yoke in the second, pressurized position.
Another object of the invention is to provide an isostatic press having a body which is driven by a linear actuator.
Another object of the invention is to provide an isostatic press which does not require flexible hose to be used to connect with the process connections. Flexible hose is not required because the process connections are affixed to passageways through the top and bottom covers which are stationary.
It is a further object of the invention to provide an isostatic press whose frame/yoke does not have to be retracted or moved in the course of loading and unloading workpieces from the pressure vessel.
It is a further object of the present invention to provide a surface upon which workpieces may be placed which is accessible from a large arc on both sides of the frame/yoke.
It is a further object of the present invention to provide an isostatic press which occupies very little floor space enabling ancillary robotic equipment and the like to be located in proximity thereto. Ancillary equipment may be robotic equipment and the like.
These and other objects of the invention will be better understood when reference is made to the Brief Description Of The Drawings, Description Of The Invention and claims which follow hereinbelow.